Biocidal compositions

ABSTRACT

A synergistic composition of biocides for the preparation of anti-fouling paint preferably containing at least one of the group of 3-iodo-2-propynyl-butyl carbamate, 3-iodo-2-propynyl-cyclohexyl carbamate, 3-iodo-2-propynyl phenyl carbamate, 3-iodo-2-propynylbenzyl carbamate, 3-iodo-2-propynyl propyl carbamate and 4-iodo-3-butynyl propyl carbamate and at least one of the group of tributyltin compounds consisting of bis(tributyltin) oxide, tributyltin fluoride, tributyltin methacrylate, tributyltin phosphate and tributyltin naphthenate. Said composition is more effective in protecting ship bottoms or underwater constructions than each component itself.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to biocidal compositions, particularlythose containing a synergistic mixture of carbamate and organotinbiocides useful for protecting materials exposed to an aquaticenvironment. This invention especially relates to the prevention andinhibition of fouling of marine structures such as boat, ship, or othervessel hulls, pilings, oil well drilling towers, and the like byorganisms commonly found in sea water.

In a preferred embodiment, the present invention relates to a biocidalcomposition containing a synergistic mixture of carbamate andtributyltin biocides. In this preferred embodiment, a marine structureis treated by coating the surface thereof with a paint containing anorganic binder and a biocidally effective amount of the mixture of (1)the carbamate compound, such as one selected from the group consistingof 3-iodo-2-propynyl propyl carbamate, 3-iodo-2-propynyl butylcarbamate, 3-iodo-2-propynyl hexyl carbamate, 3-iodo-2-propynylcyclohexyl carbamate, 3-iodo-2-propynyl phenyl carbamate,3-iodo-2-propynyl benzyl carbamate, 4-iodo-3-butynyl propyl carbamateand mixtures thereof, and (2) the tributytin compound, such as oneselected from the group consisting of bis(tributyltin) oxide,tributyltin fluoride, tributyltin methacrylate, tributyltin phosphateand tributyltin naphthenate, and mixtures thereof. In anotherembodiment, a marine structure is treated by coating its surface with acomposition containing a biocidally effective amount of either3-iodo-2-propynyl propyl carbamate or 4-iodo-3-butynyl propyl carbamateor a mixture thereof.

2. Description of Related Art

Singer U.S. Pat. No. 3,923,870 describes urethanes of1-halogen-substituted alkynes and their fungicidal activity. Thecompound 3-iodo-2-propynyl butyl carbamate (IPBC) (CAS 55406-53-6)described in U.S. Pat. No. 3,923,870 is widely used as a fungicide foraqueous and organic solvent based systems such as paints and coatings,metal cutting fluids, textile and paper coatings, inks, plastics,adhesives and the like. Research indicates that IPBC has a promisingefficacy profile against wood destroying organisms (fungi), having shownlow toxic values for common fungi. Indeed, a unique characteristic ofIPBC is its efficacy against both blue stain (ascomycetes) and generalwood destroying fungi (basidiomycetes) at a reasonable application rate.IPBC is also known as an algicide for use in fresh water and marineapplications, see U.K. Patent 2,138,292.

It also is known that organic tin compounds such as those of the generalformula:

    (CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2).sub.3 Sn-R.sup.4

where R⁴ is selected from (CH₃ CH₂ CH₂ CH₂)₃ SnO, fluoride, chloride,phosphate, acrylate methacrylate, naphthenate, hydroxide, octoate,phthalate, sulfate, maleate, fumarate, laureate, linoleate, abietate,ethanesulphonate, and the like can be used in paints to provideanti-fouling property to coatings applied to ship hulls to preventfouling by algae and other marine organisms (pests).

The prior art, however, does not provide any indication whether thecombination of the fungicide IPBC or other related carbamate fungicideswith an organic tin compound such as one or more of the above-mentionedtributyltin-type compounds would be useful for anti-fouling coatings forprotecting materials exposed to an aquatic (eg. marine) environment,such as ship hulls and other underwater constructions.

The growth of marine organisms on the submerged parts of a ship's hullincreases the frictional resistance of the hull to passage throughwater, leading to increased fuel consumption and/or a reduction in thespeed of the ship. Marine growths accumulate so rapidly that the remedyof cleaning and repainting as required in drydock is generallyconsidered too expensive. An alternative which has been practiced withincreasing efficiency over the years, is to limit the extent of foulingby applying to the hull a top coat paint incorporating anti-foulingagents. The anti-fouling agents are biocides which are freed from thesurface of the paint over a period of time at a concentration lethal tomarine organisms at the hull surface. The anti-fouling paint fails onlywhen the concentration of biocide available at the paint surface fallsbelow the lethal concentration and with modern paints up to two years ofuseful life is expected.

There are marked distinctions between the requirements for biocides indifferent environments, such as antifungal agents in house paints, freshwater algicides, and antifouling agents for marine structures exposed tosea water flora and fauna. As is known, the mildew or fungus which growson house paints and the like, utilizes the paint medium as a nutrient,or in some cases, the underlying substrate, such as wood, as thenutrient. The mycelia and fruiting bodies of the fungi contact orpenetrate the paint film and thus, through intimate contact with anyfungicides in the film (to a large extent regardless of whether thefungicides are highly soluble, slightly soluble, or insoluble in water),the fungi are destroyed. In cooling towers utilizing fresh water, slimeand algae may develop if effective compounds for combatting their growthare not present. In the case of cooling tower water, the compound shouldbe highly soluble. In paints such as exterior house paints, undergoingnormal exposure to weather, the solubility of the compound is not ascritical since the paint film is only sporadically exposed to liquidwater.

While IPBC and related carbamate compounds are known to exhibit goodfungicidal and algicidal activity, it is not known whether thesefungicides could also be used in anti-fouling coatings in combinationwith known organic tin compounds, particularly tributyltin-typecompounds, to prevent the growth of marine organisms like algae,barnacles, encrusting bryozoan, tunicates, hydroids, adherent slime orother higher developed crustaceas on submerged surfaces. Resultsobtained with anti-fouling paints when utilizing IPBC and relatedcompounds are not predictable from their effectiveness as generalbiocides, whether against bacteria, fungi, insects, etc. It also is notknown if or how long the combination would retain its efficacy as ananti-fouling biocide formulation or whether it might even be superior inoverall performance as an anti-fouling compound in comparison to theiodopropynyl carbamate-related compounds or the tributyltin-relatedcompounds by themselves.

Additionally, it is not known how the combination of one or more membersfrom each group of these compounds would affect their overall biocidal(anti-fouling) activity, for example, if used in paint to protect shiphulls from the growth of marine organisms. As is always a possibilitywhen using a combination of chemicals having diverse activities, one ofthe chemicals may impair or interfere with the activity of the other.

From the foregoing, it is apparent that the effectiveness of biocidalmaterials useful in combatting fungi, insects, bacteria, and the like innon-aqueous media, and biocides effective in combatting fungi, slime,and algae in fresh water systems, cannot be used to predict theeffectiveness of these compounds as anti-fouling agents in sea water andbrackish water capable of supporting marine life such as barnacles,slime, hydroids, "grassy" brown felt algae and the like.

Since the prior art has not disclosed or suggested combining IPBC or itsrelated carbamate compounds with organic tin compounds, and especiallythe above-mentioned tributyltin-type biocides, the prior art does notindicate what amounts of the fungicide IPBC (and its related carbamatecompounds) and of the organic tin compound, such as one or more of theabove-noted tributyltin-type biocides, are required to provide anoptimum in anti-fouling application against algae and higher developedmarine organisms. For similar reasons, it is not known what amounts ofIPBC (and its related carbamate compounds) and of the organic tincompound are needed to obtain the long-lasting efficacy needed forsuccessful anti-foulant, marine applications, or how to formulate aneffective anti-foulant composition using this biocide combination.

In this regard, there is a growing concern about the environmentaleffects caused by using the organic tin biocides at their presentcommercial levels as an anti-foulant active ingredient in coatingcompositions for aquatic (marine) applications. It has been shown that,due to the wide-spread use of tributyltin-type compounds in particular,at concentrations as high as 20 wt. % in paints for ship bottoms, thepollution of surrounding water due to leaching has reached such a levelas to cause the degradation of mussel and shell organisms. These effectshave been detected along the French-British coastline and a similareffect has been confirmed in U.S. and Far East waters. Under the mostrecent regulatory restrictions, with limited exceptions, pleasure boatsup to 25 meters long are no longer permitted to use anti-foulant paintcontaining high levels of tributyltin compounds.

Research has shown that as long as the leaching rate of tin can bemaintained at or below about 4 ug/cm² per day, aquatic life does notappear to be affected over the long term. However, it has also beenfound that to be effective for controlling marine algae, as well ashigher developed marine organisms, from the painted surface of shipbottoms, a certain minimum leaching rate of tin of about 9 to 16 ug/cm²/day is required. Usually, this higher leaching rate is achieved with aconcentration of tributyltin compound at about 15% to 20% by weight ofpaint.

Obviously, these two requirements are at odds. Authorities havereluctantly agreed that as long as there is no satisfactory substitutefor the anti-foulant organic tin active ingredients, larger ships, i.e.,those above a length of 25 meters, are still permitted to use suchcompounds to minimize fouling. As an indication of the importance of newsolutions to this age old problem, the EPA has agreed to certify within90 days new anti-foulant paints meeting the requirements of acceptablerelease rates.

DISCLOSURE OF THE INVENTION

In a first aspect, the present invention provides a composition useful,for example as a coating, for the long-term protection of materialsexposed to an aquatic (marine) environment. The composition comprises amixture of (i) an iodoalkynyl carbamate of the formula ##STR1## in whichm is 1, 2 or 3; n is 1, 2 or 3; and R is hydrogen, an unsubstituted orsubstituted alkyl, aryl, aralkyl, alkaryl, alkenyl, cycloalkyl orcycloalkenyl, or an alkoxy aryl all having from 1 to not more than 20carbon atoms and m and n may be the same or different and (ii) anorganic trihydrocarbyl tin compound of the formula ##STR2## where R¹, R²and R³ can each be an alkyl or cycloalkyl having from 1 to 6 carbonatoms or an aryl, aralkyl or alkaryl having from 6 to 12 carbon atomsand R⁴ is selected from (CH₃ CH₂ CH₂ CH₂)₃ SnO, fluoride, chloride,phosphate, methacryate, naphthenate, hydroxide, octoate, phthalate,sulfate, laureate, linoleate, abietate, and ethanesulphonate. Thecomposition is particularly useful in anti-fouling paint and iseffective for combatting fouling organisms common in sea water andbrackish water, the organisms including weeds (algae), slime, brown feltalgae, hydroids, barnacles, encrusting bryozoan, tunicates, hydroids,adherent slime and the like.

It has been found that a combination of one or more from the group of3-iodo-2-propynyl butyl carbamate (IPBC), 3-iodo-2-propynyl hexylcarbamate (IPHC), 3-iodo-2-propynyl cyclohexyl carbamate (IPCC),3-iodo-2-propynyl phenyl carbamate (IPPhC), 3-iodo-2-propynyl benzylcarbamate (IP benzyl C), 3-iodo-2-propynyl propyl carbamate (IPPC),4-iodo-3-butynyl propyl carbamate (IBPC) and/or other relatedderivatives with one or more of the tributyltin compounds represented bythe formula:

    (CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2).sub.3 Sn-R.sup.4

where R⁴ is selected from (CH₃ CH₂ CH₂ CH₂)₃ SnO, fluoride, chloride,phosphate, methacryate, naphthenate, hydroxide, octoate, phthalate,sulfate, laureate, linoleate, abietate, and ethanesulphonate provides acomposition having superior anti-foulant performance. It has beendiscovered that with this combination of ingredients, the total amountof active ingredients needed to provide satisfactory performance islower in comparison to the amount of the individually applied compoundsrequired to provide a similar anti-fouling protection. In other words,the combination of the carbamate and trihydrocarbyl tin compoundsprovides a synergistic result relative to the use of eitherindividually.

In another aspect, the present invention provides a method ofcontrolling fouling of an underwater surface of a marine structure bymarine pests which comprises applying a coating of a paint to thesurface, the paint containing a biocidally effective amount of a mixtureof at least one of the above-identified iodoalkynyl carbamates and atleast one of the above-identified organic trihydrocarbyl tin compounds.

In an alternative aspect, the method of controlling fouling employs apaint containing a biocidally effective amount of 3-iodo-2-propynylpropyl carbamate or 4-iodo-3-butynyl propyl carbamate or a mixturethereof.

In accordance with the present invention, a biocidal composition isprovided which is useful for protecting surfaces such as wood and othermaterials exposed to an aquatic (marine) environment from attack bymarine pests. In the first aspect of the invention, the compositioncontains a mixture of

a) at least one iodoalkynyl carbamate compound having a formula:##STR3## in which m is 1, 2 or 3; n is 1, 2 or 3; and R is hydrogen (H);an unsubstituted or substituted alkyl, aryl, aralkyl alkylaryl, alkenyl,cycloalkyl, or cycloalkenyl or an alkoxy aryl all having from one to notmore than 20 carbon atoms, and m and n may be the same or different, and

b) at least one trihydrocarbyl tin compound having a formula: ##STR4##where R¹, R² and R³ can each be an alkyl or cycloalkyl having from 1 to6 carbon atoms or an aralkyl or alkaryl having from 6 to 12 carbon atomsand R⁴ is selected from (CH₃ CH₂ CH₂ CH₂)₃ SnO, fluoride, chloride,phosphate, acrylate, methacrylate, naphthenate, hydroxide, octoate,phthalate, sulfate, maleate, fumarate, laureate, linoleate, abietate,and ethanesulphonate.

Suitable R substituents for the iodoalkynyl carbamate compound includealkyls such as methyl, ethyl, propyl, n-butyl, t-butyl, pentyl (amyl),hexyl, heptyl, octyl, nonyl, decyl, dodecyl, octadecyl, cycloalkyls suchas cyclohexyl, aryls, alkaryls and aralkyls such as phenyl, benzyl,tolyl, cumyl, halogenated alkyls and aryls, such as chlorobutyl andchlorophenyl, and alkoxy aryls such as ethoxyphenyl and the like. Thus,suitable carbamate compounds are selected from the group consisting of3-iodo-2-propynyl butyl carbamate (IPBC), 3-iodo-2-propynyl hexylcarbamate (IPHC), 3-iodo -2-propynyl cyclohexyl carbamate (IPCC),3-iodo-2-propynyl phenyl carbamate (IPPhC), 3-iodo-2-propynyl benzylcarbamate (IP Benzyl C), 3-iodo-2-propynyl propyl carbamate (IPPC),4-iodo-3-butynyl propyl carbamate (IBPC), 3-iodo-2-propynyl-4-chlorophenyl carbamate (IPC1PhC), 3-iodo-2-propynyl-4-chloro butyl carbamate(IPC1BC) and mixtures thereof.

A preferred group of carbamate fungicides for use with thetrihydrocarbyl tin compounds is represented by the formula: ##STR5##where n is 1 or 2 and R is propyl, butyl, hexyl, cyclohexyl, phenyl orbenzyl.

Two iodoalkynyl carbamate compounds, which have surprising efficacy forcontrolling fouling of marine structures when used alone, when used incombination or when used in admixture with trihydrocarbyl tin compoundsare 3-iodo-2-propynyl propyl carbamate (IPPC) and 4-iodo-3-butynylpropyl carbamate (IBPC).

Suitable R¹, R² and R³ substituents for the trihydrocarbyl tin compoundsare alkyls such as methyl, ethyl, propyl, butyl, pentyl (amyl) andhexyl, cycloalkyls such as cyclohexyl; aryls, aralkyls, or alkaryls suchas phenyl, benzyl and tolyl. These substituents can all be the same,such as tributyl, triphenyl and the like or can be different such asdiethylbutyl, diethylamyl, diamylmethyl, diethylphenyl, ethyldiphenyland the like. Suitable trihydrocarbyl tin compounds includetricyclohexyl-tin chloride, tributyl tin chloride, trimethyl tinchloride and triphenyl tin chloride. Preferred trihydrocarbyl tincompounds are selected from the group of tributyltin compoundsconsisting of bis (tributyltin) oxide (TBTO), tributyltin fluoride(TBTF), tributyltin methacrylate, tributyltin phosphate, tributyltinnaphthenate and mixtures thereof.

Generally, the compositions of the present invention are formulated aspaints lacquers, stains, enamels and the like, hereinafter referred togenerically as "paint", and will include a liquid vehicle (solvent) fordissolving or suspending the active biocidal ingredients and an organicbinder. The vehicle may typically contain at least one of a diluent, anemulsifier and a wetting agent.

Any conventional organic binder may be utilized in marine anti-foulingpaint incorporating the biocidal compositions of the present inventionand particularly the synergistic anti-foulant mixture of the presentinvention. Examples of trade-recognized binders are polyvinyl chlorideresins in a solvent based system, chlorinated rubbers in a solvent basedsystem, acrylic resins and methacrylate resins in solvent based oraqueous systems, vinyl chloride-vinyl acetate copolymer systems asaqueous dispersions or solvent based systems, butadiene copolymers suchas butadiene-styrene rubbers, butadiene-acrylonitrile rubbers, andbutadiene-styrene-acrylonitrile rubbers, drying oils such as linseedoil, alkyd resins, asphalt, epoxy resins, urethane resins, polyesterresins, phenolic resins and the like.

The paints commonly may contain inorganic pigments, such as titaniumdioxide, ferric oxide, silica, talc, or china clay, organic pigmentssuch as carbon black or dyes insoluble in sea water, and may containmaterials such as rosin to provide controlled release of theanti-foulant, rosin being to a very slight extent soluble in sea water.The paints may contain plasticizers, rheology characteristic modifiersand other conventional ingredients.

In still other aspects of the present invention, the compositions,particularly when formulated as paints, also are provided with otheradjuvants conventionally employed in compositions used for protectingmaterials exposed to an aquatic environment such as additionalfungicides, auxiliary solvents, processing additives such as defoamers,fixatives, plasticizers, UV-stabilizers or stability enhancers, watersoluble or water insoluble dyes, color pigments, siccatives, corrosioninhibitors, thickeners or antisettlement agents such as carboxymethylcellulose, polyarcylic acid or polymethacrylic acid, anti-skinningagents and the like. Additional fungicides used in the compositions arepreferably soluble in the liquid vehicle.

The synergistic biocidal composition of the present invention generallycomprises from about 0.1 to 10 parts by weight, more generally fromabout 0.2 to 5 parts by weight, and most often from about 0.3 to 4 partby weight of at least one trihydrocarbyl tin compound, preferably oneselected from the group consisting of bis(tributyltin) oxide,tributyltin fluoride, tributyltin methacrylate, tributyltin phosphateand tributyltin naphthenate, and mixtures thereof per part by weight ofthe iodoalkynyl carbamate compound, with the carbamate compoundpreferably being selected from the group consisting of3-iodo-2-propynyl-butyl carbamate, 3-iodo-2-propynyl hexyl carbamate,3-iodo-2-propynyl cyclohexyl carbamate, 3-iodo-2-propynyl phenylcarbamate, 3-iodo-2-propynyl benzyl carbamate, 3-iodo-2-propynyl propylcarbamate, 4-iodo-3-butynyl propyl carbamate, 3-iodo-2-propynyl-4-chlorophenyl carbamate, 3-iodo-2-propynyl-4-chloro butyl carbamate andmixtures thereof.

Compositions of the present invention can be provided as a ready-for-useproduct in the form of aqueous solutions and dispersions, oil solutionsand dispersions, emulsions, aerosol preparations and the like or as aconcentrate. The concentrate can be used as is, for example as anadditive for paint, or can be diluted prior to use with additionalsolvents or suspending agents.

When the compositions are supplied as a concentrate with the activeingredients dissolved or dispersed in a liquid vehicle or carriermaterial, the active biocidal ingredient or mixture of ingredientstypically comprises from about 0.1% by weight up to about 80% by weightof the total composition. After formulation as a paint, the preparationtypically will contain from about 0.1% by weight up to about 40% byweight, more generally from about 1.0% to about 20% by weight, and mostoften from about 1% to about 10% by weight of the active ingredient ormixture of active ingredients. A liquid vehicle normally comprises morethan about 70% by weight, and more generally above about 90% by weightof the composition when it is formulated as a paint. In someconcentrates, however, the liquid vehicle can constitute as little as 5%by weight of the composition.

The liquid vehicle is not a critical aspect of the present invention andany liquid which does not interfere with the biocidal activities of theactive ingredients and which is compatible with the disclosedapplications potentially can be used in the present invention. Suitablematerials for the liquid vehicle include water and organic solventsincluding aliphatic hydrocarbons, aromatic hydrocarbons, such as xylene,toluene, mixtures of aliphatic and aromatic hydrocarbons having boilingpoints between 100° and 320° C., preferably between 150° and 230° C.;high aromatic petroleum distillates, e.g., solvent naptha, distilled taroil and mixtures thereof; alcohols such as butanol, octanol and glycols;vegetable and mineral oils; ketones such as acetone; petroleum fractionssuch as mineral spirits and kerosene, chlorinated hydrocarbons, glycolesters, glycol ester ethers, and the like. The liquid vehicle maycontain at least one polar solvent, such as water, in admixture with anoily or oil-like low-volatility organic solvent, such as the mixture ofaromatic and aliphatic solvents found in white spirits, also commonlycalled mineral spirits.

The liquid vehicle also may commonly include an emulsifier, a wettingagent, a dispersing agent or other surface active agent. Examples ofsuitable emulsifiers are the nonylphenol-ethylene oxide ethers, andpolyoxyethylene sorbitol esters or polyoxyethylene sorbitan esters offatty acids. For example, a useful formulation may contain the mixtureof the active biocidal constituents dissolved in an organic solvent suchas mineral spirits which in turn is emulsified with the aid of asuitable emulsifier in water as the primary liquid vehicle.

An aerosol preparation according to the invention is obtained in theusual manner by incorporating the active ingredients dissolved orsuspended in a suitable solvent, in a volatile liquid suitable for useas a propellant, for example the mixture of chlorine and fluorinederivatives of methane and ethane commercially available under thetrademark "Freon", or compressed air.

The balance of the compositions may include additional ingredients knownto be useful in preservatives and coatings for aquatic applications andrelated products. Such ingredients include fixatives such ascarboxymethylcellulose, polyvinyl alcohol, a paraffin and the like,co-solvents, such as ethylglycol acetate and methoxypropyl acetate andplasticizers such as benzoic acid esters and phthlates, e.g., dibutylphthalate, dioctyl phthalate and didodecyl phthalate. Optionally dyes,color pigments, corrosion inhibitors, chemical stabilizers or siccatives(dryers) such as cobalt octate and cobalt naphthenate also may beincluded depending on specific applications.

Such additional ingredients are not essential to the practice of thepresent invention but are included in particular formulations tooptimize overall effectiveness and ease of application. The specificexamples of suitable constituents for specific preparations asenumerated above are not meant to be limiting and a wide variety ofother possible ingredients will be recognized by those skilled in theart. Similarly, the quantity of such additional ingredients in anyformulation is not critical. They generally can be used in an amountconventionally employed for products designed to be used in applicationsfor protecting materials exposed to an aquatic environment. Normally,the totally formulated composition may contain from about 0.1% to 95% byweight, and more usually from about 1% to 50% by weight of theseadditional ingredients on a total solids basis.

Biocidal compositions of the present invention can be applied by any ofthe techniques known in the art including brushing, spraying, rollcoating, dipping and the like. Generally, to obtain effective treatment,it should be sufficient to apply the composition in an amount to providebetween about 20 to 180 grams of the active ingredient or mixture ofactive ingredients per square meter of surface area to be treated (about0.0040 to 0.037 pound per square foot), with an amount of about 80 to120 g/m² (about 0.016 to 0.025 lb/ft²) being more typical. Of course,higher rates of application can be used if desired.

Compositions of the present invention can be prepared simply by mixingthe various ingredients at a temperature at which they are not adverselyaffected, e.g., at a temperature of from about -5° C. to 80° C.,preferably at a temperature of from about 10° C. to 45° C. and at apressure of 450 mmHg to 900 mmHg, preferably at about 650 mmHg to 850mmHg. Preparation conditions are not critical. Equipment and methodsconventionally employed in the manufacture of paint and similarcompositions can be advantageously employed.

In preliminary tests over a period of 7.5 weeks during the summer, whichis a high growing season for marine organisms, test panels were coatedwith a representative paint used as a base for preparing anti-foulingpaints and were placed in seawater. The base paint was mixed with theindividual compounds listed in the table below up to a concentration of10 wt. %. The individual test results are listed in the following table:

    ______________________________________                                                 Use                                                                  Compound Level      4 Weeks  6 Weeks 7.5 Weeks                                ______________________________________                                        TBTO     10%        clean    clean   m. growth                                TBTF     10%        clean    clean   m. growth                                IPBC     10%        clean    sl. growth                                                                            h. growth                                IPCC     10%        clean    sl. growth                                                                            h. growth                                IPPhC    10%        clean    sl. growth                                                                            h. growth                                IP Benzyl C                                                                            10%        clean    sl. growth                                                                            h. growth                                TBTO/IPBC                                                                              5% + 5%    clean    clean   clean                                    TBTO/IPBC                                                                              3.5% + 6.5%                                                                              clean    clean   clean                                    TBTO/IPBC                                                                              3.5% + 3.5%                                                                              clean    clean   clean                                    TBTO/IPBC                                                                              2% + 8%    clean    m. growth                                                                             sl. growth                               TBTO/IPBC                                                                              8% + 2%    clean    clean   m. growth                                TBTO/IPBC                                                                              6.5% + 3.5%                                                                              clean    clean   clean                                    ______________________________________                                         Note: m = moderate, sl = slight, h = heavy                               

The table shows slight to heavy growth for IPBC and its derivatives aswell as moderate to slight growth for the tributyltin derivatives usedat a concentration of 10 wt. % in the paint composition. After 7.5weeks, however, in all instances the individual biocides showed signs offailure at use levels of 10 wt. %.

Surprisingly, the synergistic combination of the present inventionshowed a superior efficacy when used in the same total amount. Suitablepoints can be made up using a ratio of 1 wt. % TBTO and 10 wt. % IPBC upto 10 wt. % TBTO and 1 wt. % IPBC. Primarily, when IPBC and TBTO wereused in a ratio of 1:4 to 4:1 the mixture showed excellent performancewith an optimum close to a ratio of 1:1 by weight.

With a second test series the ratio of 1:4 to 4:1 was evaluated indecreasing total amount of the sum of both biocides. Even at a total of7% of active ingredient preferably in the ratio of 1:1 added to astandard coating (paint) for ship bottoms, the 7.5 week test periodcontinued to indicate superior activity, in comparison to TBTO at ahigher level. These experiments clearly show that the combination ofIPBC and TBTO is more effective than IPBC or TBTO applied on their ownas anti-fouling biocides, indicating a synergistic effect.

Preferably, the two components are premixed before use to form aconcentrate in the ratio of 1:4 to 4:1 in a concentration up to a totalof 80% dissolved in suitable auxiliary solvents like Xylol or the liketo provide easy and homogeneous distribution in the paint, which isintended to perform as an anti-fouling coating.

The following examples are illustrative of compositions according to thepresent invention and are not intended to be limiting.

    ______________________________________                                        Example 1:                                                                    ______________________________________                                        3-iodo-2-propynyl butyl carbamate                                                                   5%                                                      tributyltin oxide     5%                                                      auxiliary solvents    3.3%                                                    vinyl acrylic paint   86.7%                                                   ______________________________________                                    

    ______________________________________                                         Example 2:                                                                   ______________________________________                                        3-iodo-2-propynyl butyl carbamate                                                                   4%                                                      bis (tributyltin) oxide                                                                             5%                                                      auxiliary solvent     4%                                                      vinyl acrylic copolymer paint                                                                       87%                                                     ______________________________________                                    

    ______________________________________                                         Example 3:                                                                   ______________________________________                                        3-iodo-2-propynyl butyl carbamate                                                                   3.5%                                                    bis (tributyltin) oxide                                                                             3.5%                                                    auxiliary solvent     3.0%                                                    vinyl acrylic paint   90.0%                                                   ______________________________________                                    

    ______________________________________                                         Example 4:                                                                   ______________________________________                                        3-iodo-2-propynyl butyl carbamate                                                                   6%                                                      bis (tributyltin) oxide                                                                             3.5%                                                    auxiliary solvent     3.3%                                                    vinyl acrylic copolymer paint                                                                       87.2%                                                   ______________________________________                                    

    ______________________________________                                         Example 5:                                                                   ______________________________________                                        3-iodo-2-propynyl butyl carbamate                                                                   4%                                                      bis (tributyltin) oxide                                                                             4%                                                      auxiliary solvent     4%                                                      oil based alkyd resin paint                                                                         88.0%                                                   ______________________________________                                    

    ______________________________________                                         Example 6:                                                                   ______________________________________                                        3-iodo-2-propynyl butyl carbamate                                                                   5.0%                                                    bis (tributyltin) oxide                                                                             5.0%                                                    auxiliary solvent     4.0%                                                    pigments              10.0%                                                   epoxy based paint     76.0%                                                   ______________________________________                                    

    ______________________________________                                         Example 7:                                                                   ______________________________________                                        3-iodo-2-propynyl butyl carbamate                                                                   4.0%                                                    bis (tributyltin) oxide                                                                             6.0%                                                    auxiliary solvent     3.0%                                                    pigments              10.0%                                                   chlorinated rubber based paint                                                                      77.0%                                                   ______________________________________                                    

    ______________________________________                                         Example 8:                                                                   ______________________________________                                        3-iodo-2-propynyl butyl carbamate                                                                   5.0%                                                    bis (tributyltin) oxide                                                                             5.0%                                                    auxiliary solvents    5.0%                                                    acrylic based paint   85.0%                                                   ______________________________________                                    

    ______________________________________                                         Example 9:                                                                   ______________________________________                                        3-iodo-2-propynl butyl carbamate                                                                    6.0%                                                    tributyltin oxide     4.0%                                                    auxiliary solvent     6.0%                                                    urethane based paint  84.0%                                                   ______________________________________                                    

While certain specific embodiments of the invention have been describedwith particularity herein, it will be recognized that variousmodifications thereof will occur to those skilled in the art and it isto be understood that such modifications and variations are to beincluded within the purview of this application and the spirit and scopeof the appended claims.

I claim:
 1. A biocidal composition useful for retarding the fouling ofships and underwater constructions comprising a synergistic mixtureof:a) at least one iodoalkynyl carbamate compound having a formula:##STR6## in which m is 1, 2, or 3; n is 1, 2, or 3; and R is hydrogen(H), an unsubstituted or substituted alkyl, aryl, aralkyl, alkylaryl,alkenyl, cycloalkyl, or cycloalkenyl or an alkoxy aryl all having fromone to not more than 20 carbon atoms, and m and n may be the same ordifferent, and b) at least one trihydrocarbyl tin compound having aformula: ##STR7## where R¹, R² and R³ can be an alkyl or cycloalkylhaving from 1 to 6 carbon atoms or an aralkyl or alkaryl having from 6to 12 carbon atoms and R⁴ is selected from (CH₃ CH₂ CH₂ CH₂)₃ SnO,fluoride, chloride, phosphate, acrylate, methacrylate, naphthenate,hydroxide, octoate, phthalate, sulfate, maleate, fumarate, laureate,linoleate, abietate, and ethanesulphonate having a weight ratio ofcarbamate to trihydrocarbyl tin of from about 1:10 to 10:1.
 2. Acomposition according to claim 1 wherein the carbamate compound isselected from the group consisting of 3-iodo-2-propynyl propylcarbamate, 3-iodo-2-propynyl butyl carbamate, 3-iodo-2-propynyl hexylcarbamate, 3-iodo-2-propynyl cyclohexyl carbamate, 3-iodo-2-propynylphenyl carbamate, 3-iodo-2-propynyl benzyl carbamate, 4-iodo-3-butynylpropyl carbamate, 3-iodo-2-propynyl-4-chloro phenyl carbamate,3-iodo-2-propynyl-4-chloro butyl carbamate and mixtures thereof.
 3. Acomposition according to claim 2 wherein R¹, R² and R³ are butyl.
 4. Acomposition according to claim 3 wherein the trihydrocarbyl tin compoundselected from the group consisting of bis(tributyltin) oxide,tributyltin fluoride, tributyltin methacrylate, tributyltin phosphate,tributyltin naphthenate, and mixtures thereof.
 5. A compositionaccording to claim 4 having a weight ratio of carbamate totrihydrocarbyltin of from 1:4 to 4:1.
 6. A composition according toclaim 1 wherein said mixture comprises between 0.1% and 80% by weight ofsaid composition.
 7. A composition according to claim 6 wherein saidmixture comprises between 1% and 20% by weight of said composition. 8.An antifouling paint containing the biocidal composition of claim 1 inadmixture with a solvent and binder.
 9. An antifouling paint containingthe biocidal composition of claim 4 in admixture with a solvent andbinder.
 10. A paint according to claim 8 or 9 wherein the solvent isselected from the group consisting of water, mixtures of aliphatic andaromatic hydrocarbons, xylene, toluene, solvent naptha, distilled taroil, butanol, octanol, glycols, vegetable oil, mineral oil, mineralspirits, kerosene, acetone and mixtures thereof.
 11. A paint accordingto claim 8 or 9 wherein the binder is selected from the group consistingof glycol esters, glycol esterethers, alkyd resins, acrylic resins,methacrylate resins, polyvinyl chloride resins, butadiene copolymers,epoxy resins, chlorinated rubbers, urethane resins, polyester resins,phenolic resins and mixtures thereof.
 12. The paint of claim 8 or 9containing from about 1.0 to 20% by weight of said mixture of carbamatecompound and trihydrocarbyl tin compound.
 13. The paint of claim 9containing at least one of a dye and a pigment.
 14. A method forretarding fouling of an underwater surface of a marine structure bymarine pests which comprises applying a coating of a paint to saidsurface, said paint containing a biocidally effective amount of thecomposition of claim 1 in admixture with a solvent and a binder.
 15. Amethod for retarding fouling of an underwater surface of a marinestructure by marine pests which comprises applying a coating of a paintto said surface, said paint containing a biocidally effective amount ofthe composition of claim 4 in admixture with a solvent and a binder.